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2 fuel pumps?

COCHEV

COCHEV

1/2 ton status
Joined
Jul 9, 2002
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Location
Washougal WA
So when picked up my latest burb I noticed the familiar sound of an external electric fuel pump. Didn't think much of it, my last burb had one. However, I noticed it still had the mechanical one on the block. I figured PO must have been lazy and left it on there...

Fast forward to tonight. I'm under the dash removing the usual spaghetti one finds and I trace this unmarked toggle switch back to the fuel pump:what: so I fired it up and shut off the pump and she runs just fine. Drove it to Napa and back, no different than before

So for a week I've been driving around with 2 fuel pumps going:doah: Anyone know why someone would run such a setup? All I can think of is for backup if the mechanical one goes out...
 
COCHEV said:
All I can think of is for backup if the mechanical one goes out...
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this is the exact reason I have a second frame rail mounted one back by my tank...........that and a nice removable cover to get to the one in the tank from under the carpet in the back because mine is TBI :whistle:
 
Could be too a secondary to prevent starvation when craeling or....
 
Pretty sure the burb has never been a crawler. And I can't say that I've ever had vapor lock problems or any other problems with the mechanicals pumps. But maybe that's just me.
 
COCHEV said:
Pretty sure the burb has never been a crawler. And I can't say that I've ever had vapor lock problems or any other problems with the mechanicals pumps. But maybe that's just me.
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I had the problem on the wife's 1989 Jeep Grand Wagoneer and as soon as I wired in an electric pump at the tank on a switch the fuel issue never happened again. I also found that with the carb, I never lost pressure when at extreme angles up/down hill........:waytogo:
 
that mechanical pump next to the block on a HOT summer day and heavy extended driving can boil off the fuel going through it pretty quickly........
 
JPOutfitters said:
I had the problem on the wife's 1989 Jeep Grand Wagoneer and as soon as I wired in an electric pump at the tank on a switch the fuel issue never happened again. I also found that with the carb, I never lost pressure when at extreme angles up/down hill........:waytogo:
Click to expand...

So you were running both pumps at once?
 
COCHEV said:
So you were running both pumps at once?
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on the Grand Wagoneer, I would flip the switch if it started to lose power/fuel pressure on a hot day driving up/down the canyon we lived in. The electric pump would maintain pressure through the manual pump. I would turn it off when it wasn't needed.
 
Very interesting...never thought to run the both of these in series. Good to have these blogs to learn from.
Never occured to me vapor lock. Shows how long its been since playing around with motors and all.

Somewhat related, many years ago, purchased an intake/carb setup for the 72' before parking her. Never dreamed it would be 11 years later lol. Looks like a raggy old carb that has weathered....sad!!
 
JPOutfitters said:
on the Grand Wagoneer, I would flip the switch if it started to lose power/fuel pressure on a hot day driving up/down the canyon we lived in. The electric pump would maintain pressure through the manual pump. I would turn it off when it wasn't needed.
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Good info, thanks! I was going to yank it. I'll just clean up the wires and use a better switch
 
Update : so I drove to work today on the mechanical pump only. It was just fine in stop and go traffic, but on grade on the freeway she started to sputter out. So I flipped on the electric pump and it ran fine. So...in my mind I need to remedy the mechanical pump. The motor is box stock puny 80s 350, 40 degree morning. No reason I shouldn't be able to run a stock mechanical pump all day long
 
COCHEV said:
Update : so I drove to work today on the mechanical pump only. It was just fine in stop and go traffic, but on grade on the freeway she started to sputter out. So I flipped on the electric pump and it ran fine. So...in my mind I need to remedy the mechanical pump. The motor is box stock puny 80s 350, 40 degree morning. No reason I shouldn't be able to run a stock mechanical pump all day long
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You're absolutely right! Must have decided to put the electric pump in it instead of replacing the mechanical altogether then. Personally I would replace the mechanical but leave that electric one in as a back up plan. I was stranded 5 miles from a flat road on a jeep trail most people couldn't believe I was on in my Burb when my in tank pump went out. That will never happen to me again! ;-)
 
I like the back up pump idea now too. So you don't think that the mechanical pump pulling through the electric pump when its off causes any flow issues?
 
So you don't think that the mechanical pump pulling through the electric pump when its off causes any flow issues?
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Yup..... I would be very suspicious of this setup....

The right way to do it would be to have the pumps in a paralleled set up not series-ed, and have a check valve in the outlet line of each pump...that way each pump would have full unrestricted flow..... tank to carb

as you said,,,, the mechanical pump must now pull the fuel through the electric pump...
 
COCHEV said:
I like the back up pump idea now too. So you don't think that the mechanical pump pulling through the electric pump when its off causes any flow issues?
Click to expand...

I had someone raise this question before as well and had several people comment that it would be "suspicious" or a definite "issue" with flow. So I hooked up a flow and pressure gauge setup without the extra pump and after the extra pump and found a small loss that was so minimal that I went ahead and tested a few different fuel filters and found several different types of filters that caused more of a change in flow and pressure then the electric pump I have inline. It was so minimal that the benefit outweighs the adverse.

You could always buy a couple "T" shutoff valves and put a series in place as a bypass. I'm thinking I might do that now too just because it makes sense and adds to the "cool" factor!
 
Pretty sure all I've got for a filter is the one inside the q jet. I'll have to investigate more this weekend
 
So I haven't had a bunch of time to spend on this due to replacing the heater core last week, but I'm pretty sure this wasn't helping matters...

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